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AM4376: Direct RMII connection to switch

Tony Spagnolia1
Prodigy 190 points

Part Number: AM4376

We were told the AM4376 needs a PHY at the lowest MDIO address in order for the ROM code to negotiate and broadcast a BOOTP message. However, we have a board with a direct RMII connection to a KSZ8567 switch and no MDIO interface that broadcasts BOOTP messages upon booting. We need to understand how the ROM code is working for this situation.

The KSZ8567 switch is strapped on reset to be 100Mbps Ethernet, auto-negotiate, enable flow control, forward packets and output the RMII 50 MHZ clock to the AM4376. The port used is also the in-band management port of the switch. 

Is the AM4376 ROM code performing the negotiation strictly over the link layer and then broadcasting the BOOTP? Or is the ROM code actually using in band management to set up the link prior to initiating the BOOTP message? 

  • 0
    TI__Guru**** 393215 points

    Hi,

    I am sorry, direct MAC-to-MAC connections are not an use case supported by TI. This has been posted multiple times on this forum. 

  • 0 in reply to Biser Gatchev-XID
    TI__Mastermind 41510 points

    Hi,

    Answering the portion of the question concerning what the ROM is doing when configured for networking boot mode. The ROM is not performing any negotiation using in band management as it does not have that capability. The ROM is doing what the TRM is describing for network boot mode in that it will look for the lowest addressed PHY on the MDIO for the CPSW interface. If no PHY is found the boot process does not abort but will continue on to send BOOTP messages even though it did not find a PHY.

    Best Regards,

    Schuyler